There are reasonable grounds for believing that tumors may generate a steady ion current in the surrounding tissue and fluid. This current would consist of injury current and/or liquid-junction current. In principle, the detection of this steady current with surface (skin) electrodes could reveal the presence of the underlying tumor, in a non-invasive way. However, steady potentials originating in the skin will interfere with this detection, hence pose a practical difficulty. Recent measurements of the steady current generated by breast tumors, using surface electrodes, show some electrical activity from the tumors; there is large scatter supposedly due to the interfering skin potentials. It is proposed here to again measure the steady current generated by breast tumors, but the magnetic field produced by the current will be measured instead of the surface potential. The magnetic field is free of skin interference. Successful magnetic measurements of another form of injury current have already been made, due to injured canine hearts; this current was measured noninvasively around the intact canine torso. The work proposed here is a two-year pilot project, in which magnetic measurements will be made over the chests of ten normal men and ten normal women (as controls), then of ten breast-tumor patients. These measurements will be made in the MIT magnetically-shielded room using a superconducting detector. Computer techniques will be used to aid in the analysis of the measured magnetic fields, in order to localize the current sources. If magnetic detection of steady currents from tumors is found to be feasible, an assessment will be made of the clinical possibilities of this new technique.